"Both programs offer a cost-effective way to promote healthy behaviors, such as exercise," study co-author Melissa Napolitano of Temple University said in a statement.

A program was designed to encourage participants to reach the national guidelines for physical activity at 150 minutes a week. Feedback -- pointing out areas for improvement and recognizing successful efforts -- was delivered to two groups either by phone or mail and compared to the results of a control group.

At six months, the print feedback group and telephone feedback group reported 129 and 123 minutes of physical activity, respectively. At 12 months, those in the print program reported 160 minutes of physical activity a week, compared with 100 minutes in the phone group.

Feedback in print may be more effective long-term than feedback delivered via phone, according to the study published in the July issue of Health Psychology.

Napolitano conducted the research when she was at The Miriam Hospital and Brown Medical School in Providence, R.I.